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Gaseous sulfuric acid (H2SO4) is known as one of the key precursors for atmospheric new particle formation (NPF) processes, but its measurement remains challenging. Therefore, a proxy method that is able to derive gaseous sulfuric acid concentrations from parameters that can be measured relatively easily and accurately is highly desirable for the atmospheric chemistry community. Although such methods are available for clean atmospheric environments, a proxy that works well in a polluted atmosphere, such as that found in Chinese megacities, is yet to be developed. In this study, the gaseous sulfuric acid concentration was measured in February–March 2018, in urban Beijing using a nitrate based – long time-of-flight chemical ionization mass spectrometer (LToF-CIMS). A number of atmospheric parameters were recorded concurrently including the ultraviolet radiation B (UVB) intensity, the concentrations of O3, NOx (sum of NO and NO2), SO2, and HONO, and aerosol particle number size distributions. A proxy for atmospheric daytime gaseous sulfuric acid concentration was derived via a statistical analysis method using the UVB intensity, [SO2], the condensation sink (CS), [O3], and [HONO] (or [NOx]) as the predictor variables, where square brackets denote the concentrations of the corresponding species. In this proxy method, we considered the formation of gaseous sulfuric acid from reactions of SO2 and OH radicals during the daytime, and the loss of gaseous sulfuric acid due to its condensation onto the preexisting particles. In addition, we explored the formation of OH radicals from the conventional gas-phase photochemistry using O3 as a proxy and from the photolysis of HONO using HONO (and subsequently NOx) as a proxy. Our results showed that the UVB intensity and [SO2] are dominant factors in the production of gaseous sulfuric acid, and that the simplest proxy could be constructed with the UVB intensity and [SO2] alone. When the OH radical production from both homogenously and heterogeneously formed precursors were considered, the relative errors were reduced by up to 20 %.

Secondary aerosol formation in the aging process of primary emission is the main reason for haze pollution in eastern China. Pollution evolution with photochemical age was studied for the first time at a comprehensive field observation station during winter in Beijing. The photochemical age was used as an estimate of the time scale attributed to the aging process and was estimated from the ratio of toluene to benzene in this study. A low photochemical age indicates a fresh emission. The photochemical age of air masses during new particle formation (NPF) days was lower than that on haze days. In general, the strongest NPF events, along with a peak of the formation rate of 1.5 nm(J(1.5)) and 3 nmparticles (J(3)), were observed when the photochemical age was between 12 and 24 h while rarely took place with photochemical ages less than 12 h. When photochemical age was larger than 48 h, haze occurred and NPF was suppressed. The sources and sinks of nanoparticles had distinct relation with the photochemical age. Our results show that the condensation sink (CS) showed a valley with photochemical ages ranging from 12 to 24 h, while H2SO4 concentration showed no obvious trend with the photochemical age. The high concentrations of precursor vapours within an air mass lead to persistent nucleation with photochemical age ranging from 12 to 48 h in winter. Coincidently, the fast increase of PM2.5 mass was also observed during this range of photochemical age. Noteworthy, CS increased with the photochemical age on NPF days only, which is the likely reason for the observation that the PM2.5 mass increased faster with photochemical age on NPF days compared with other days. The evolution of particles with the photochemical age provides new insights into understanding how particles originating from NPF transform to haze pollution. (C) 2020 Elsevier B.V. All rights reserved.

New Particle Formation (NPF) is regularly observed to occur in heavily polluted Chinese megacities. However, in these NPF events, the survival probability of small clusters into larger aerosol particles is higher than theoretically predicted. One explanation for this could be that the loss rate of clusters due to scavenging by pre-existing particles, which is described by condensation sink, is lower than expected. In this study, we describe the loss of clusters due to condensation sink by using heterogeneous nucleation theory, and investigate if ineffectiveness of heterogeneous nucleation can result in a significantly lowered effective condensation sink. We find that in principle it is possible that due to properties of the system there is no heterogeneous nucleation, and this can significantly influence the magnitude of effective condensation sink and thus increase the survival probability of clusters.

The climate and air quality effects of aerosol particles depend on the number and size of the particles. In urban environments, a large fraction of aerosol particles originates from anthropogenic emissions. To evaluate the effects of different pollution sources on air quality, knowledge of size distributions of particle number emissions is needed. Here we introduce a novel method for determining size-resolved particle number emissions, based on measured particle size distributions. We apply our method to data measured in Beijing, China, to determine the number size distribution of emitted particles in a diameter range from 2 to 1000 nm. The observed particle number emissions are dominated by emissions of particles smaller than 30 nm. Our results suggest that traffic is the major source of particle number emissions with the highest emissions observed for particles around 10 nm during rush hours. At sizes below 6 nm, clustering of atmospheric vapors contributes to calculated emissions. The comparison between our calculated emissions and those estimated with an integrated assessment model GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) shows that our method yields clearly higher particle emissions at sizes below 60 nm, but at sizes above that the two methods agree well. Overall, our method is proven to be a useful tool for gaining new knowledge of the size distributions of particle number emissions in urban environments and for validating emission inventories and models. In the future, the method will be developed by modeling the transport of particles from different sources to obtain more accurate estimates of particle number emissions.

Top-down ultraviolet photodissociation (UVPD) allows greater sequence coverage than any other currently available method, often fracturing the vast majority of peptide bonds in whole proteins. At the same time, UVPD can be used to dissociate noncovalent complexes assembled from multiple proteins without breaking any covalent bonds. Although the utility of these experiments is unquestioned, the mechanism underlying these seemingly contradictory results has been the subject of many discussions. Herein, some fundamental considerations of photochemistry are briefly summarized within the context of a proposed mechanism that rationalizes the experimental results obtained by UVPD. Considerations for future instrument design, in terms of wavelength choice and power, are briefly discussed. Graphical Abstract ᅟ.

The limb darkening and center-to-limb variation of the continuum polarization is calculated for a grid of one-dimensional stellar model atmospheres and for a wavelength range between 300 and 950 nm. Model parameters match those of the transiting stars taken from the NASA exoplanet archive. The limb darkening of the continuum radiation for these stars is shown to decrease with the rise in their effective temperature. For the lambda = 370 nm wavelength, which corresponds to the maximum of the Johnson-Cousins UX filter, the limb darkening values of the planet transiting stars lie in a range between 0.03 and 0.3. The continuum linear polarization depends not only on the effective temperature of the star but also on its gravity and metallicity. Its value decreases for increasing values of these parameters. In the UX band, the maximum linear polarization of stars with transiting planets amounts to 4%, while the minimum value is approximately 0.3%. The continuum limb darkening and the linear polarization decrease rapidly with wavelength. At the R band maximum (lambda = 700 nm), the linear polarization close to the limb is in fact two orders of magnitude smaller than in the UX band. The center- to-limb variation of the continuum intensity and the linear polarization of the stars with transiting planets can be approximated, respectively, by polynomials of the fourth and the sixth degree. The coefficients of the polynomials, as well as the IDL procedures for reading them, are available in electronic form. It is shown that there are two classes of stars with high linear polarization at the limb. The first one consists of cold dwarfs. Their typical representatives are HATS-6, Kepler-45, as well as all the stars with similar parameters. The second class of stars includes hotter giants and subgiants. Among them we have CoRoT-28, Kepler-91, and the group of stars with effective temperatures and gravities of approximately 5000 K and 3.5, respectively.

Plant-derived natural products have long been considered a valuable source of lead compounds for drug development. Natural extracts are usually composed of hundreds to thousands of metabolites, whereby the bioactivity of natural extracts can be represented by synergism between several metabolites. However, isolating every single compound from a natural extract is not always possible due to the complex chemistry and presence of most secondary metabolites at very low levels. Metabolomics has emerged in recent years as an indispensable tool for the analysis of thousands of metabolites from crude natural extracts, leading to a paradigm shift in natural products drug research. Analytical methods such as mass spectrometry (MS) and nuclear magnetic resonance (NMR) are used to comprehensively annotate the constituents of plant natural products for screening, drug discovery as well as for quality control purposes such as those required for phytomedicine. In this review, the current advancements in plant sample preparation, sample measurements, and data analysis are presented alongside a few case studies of the successful applications of these processes in plant natural product drug discovery.

Two-photon light-sheet microscopy (2P-SPIM) provides a unique combination of advantages for fast and deep fluorescence imaging in live tissues. Detecting coherent signals such as second-harmonic generation (SHG) in 2P-SPIM in addition to fluorescence would open further imaging opportunities. However, light-sheet microscopy involves an orthogonal configuration of illumination and detection that questions the ability to detect coherent signals. Indeed, coherent scattering from micron-sized structures occurs predominantly along the illumination beam. By contrast, point-like sources such as SHG nanocrystals can efficiently scatter light in multiple directions and be detected using the orthogonal geometry of a light-sheet microscope. This study investigates the suitability of SHG light-sheet microscopy (SHG-SPIM) for fast imaging of SHG nanoprobes. Parameters that govern the detection efficiency of KTiOPO4 and BaTiO3 nanocrystals using SHG-SPIM are investigated theoretically and experimentally. The effects of incident polarization, detection numerical aperture, nanocrystal rotational motion, and second-order susceptibility tensor symmetries on the detectability of SHG nanoprobes in this specific geometry are clarified. Guidelines for optimizing SHG-SPIM imaging are established, enabling fast in vivo light-sheet imaging combining SHG and two-photon excited fluorescence. Finally, microangiography was achieved in live zebrafish embryos by SHG imaging at up to 180 frames per second and single-particle tracking of SHG nanoprobes in the blood flow., ACS Photonics, 7 (4), ISSN:2330-4022

Nd3+-doped nanoparticles have recently emerged as very attractive multifunctional systems with potential for simultaneous bio-imaging and thermal sensing, due to near-infrared excitation and emission within the first (700-980 nm)and second (1000-1400 nm)biological windows. However, while these nanoparticles have been already used for thermal sensing in the first biological window very few studies concern the second biological window. Here, we show that upon 808 nm excitation a thermometer consisting of (Gd1-xNdx)(2)O-3(x=0.020, 0.028and 0.064)nanospheres exhibits a thermal sensitivity of 0.23 +/- 0.03% K-1 at 303 K, operating in the second transparent near infrared biological window. This sensitivity value is achieved by defining the thermometric parameter as the ratio between the integrated intensity of all the transitions originated from the (4)F(3/2)highest-energy Stark component and all the transitions from the (4)F(3/2)lowest-energy. (C) 2016 Elsevier B.V. All rights reserved.

We have tested several DFT protocols, at the non-relativistic and relativistic ZORA (scalar and spin–orbit) levels, for the calculation of the 113Cd chemical shifts, δ(113Cd), for a number of cadmium complexes accounting for both different local coordination environments on the metal center, involving N, O and S ligands, and different geometrical arrangements. Moreover, suitable models as reference compounds for δ(113Cd) evaluation have been set up in order to propose a complete computational approach to calculate δ(113Cd) for cadmium complexes. Inclusion of relativistic corrections did not lead to any sensible improvement in the quality of results and, in this context, non-relativistic method, namely: B3LYP/Sadlej(Cd); 6-31g(d,p) (light atoms), showed to be the best approach to calculate δ(113Cd) for the classes of compounds investigated.

An experimental study of laser-produced plasmas is performed by irradiating a planar tin target by laser pulses, of 4.8 ns duration, produced from a KTP-based 2-µm-wavelength master oscillator power amplifier. Comparative spectroscopic investigations are performed for plasmas driven by 1-µm- and 2-µm-wavelength pulsed lasers, over a wide range of laser intensities spanning 0.5 − 5 × 1011 W/cm 2. Similar extreme ultraviolet (EUV) spectra in the 5.5–25.5 nm wavelength range and underlying plasma ionicities are obtained when the intensity ratio is kept fixed at I1µm/I2µm = 2.4(7). Crucially, the conversion efficiency (CE) of 2-µm-laser energy into radiation within a 2% bandwidth centered at 13.5 nm relevant for industrial applications is found to be a factor of two larger, at a 60 degree observation angle, than in the case of the denser 1-µm-laser-driven plasma. Our findings regarding the scaling of the optimum laser intensity for efficient EUV generation and CE with drive laser wavelength are extended to other laser wavelengths using available literature data.

Rate coefficients have been measured for the reaction of CH radicals with formaldehyde, CH$_{2}$O, over the temperature range 31 - 133 K using a pulsed Laval nozzle apparatus combined with pulsed laser photolysis and laser induced fluorescence spectroscopy. The rate coefficients are very large and display a distinct decrease with decreasing temperature below 70 K, although classical collision rate theory fails to reproduce this temperature dependence. The measured rate coefficients have been parameterized and used as input for astrochemical models for both dark cloud and AGB stellar outflow scenarios. The models predict a distinct change (up to a factor of two) in the abundance of ketene, H$_{2}$CCO, which is the major expected molecular product of the CH + CH$_{2}$O reaction., 17 pages, 9 Figures, 5 Tables, Accepted for publication in The Astrophysical Journal

The next generation of lithography machines uses extreme ultraviolet (EUV) light originating from laser-produced plasma (LPP) sources, where a small tin droplet is ionized by an intense laser pulse to emit the requested light at 13.5 nm. Numerous irradiation schemes have been explored to increase conversion efficiency (CE), out of which a double-pulse approach comprising a weak picosecond Nd:YAG pre-pulse followed by a powerful pulse is considered to be very promising [1]. Nevertheless, even for such CE-optimized schemes, ion debris ejected from the plasma with kinetic energies up to several keV remain a factor that hampers the maximum performance of LPP sources. In this letter we propose a novel pre-pulse scheme consisting of a picosecond pulse pair at 1064 nm, which decreases the amount of undesirable fast ions, avoids back-reflections to the lasers and enables one to tailor the target shape., 12 pages, 3 figures, 45 references

The continuous wave (CW) and passively Q-switched (PQS) performances of diode-pumped Nd:(LaxGd1-x)(3)Gd5O12 (Nd:LaGGG) at 1.33 mu m are achieved for the first time to our knowledge. The maximum CW output power of 5.1 W is obtained with the optical-optical conversion efficiency of 25.3% and the slope efficiency of 26.6%. In the PQS operation, by using the V3+:YAG crystal as the saturable absorber, the maximum average output power, shortest pulse width, largest pulse energy, and highest peak power are measured to be 1.1 W, 27.54 ns, 75.78 mu J, and 2.44 kW, respectively.

Condensation particle counter (CPC) technology has continued to evolve, with the introduction of several new instruments over the last several years. An important aspect in the characterization of these instruments is the measurement of their time response. Yet there is no standardly accepted approach for this measurement. Here we evaluate different classically used methods for determining CPC time response, and present the potential pitfalls associated with these approaches. Further, we introduce a new simple definition for the term response time, E, which is based on the first-order systems response, while providing a practical definition by corresponding to approximate to 95% change in concentration. We also present results for various commonly used CPCs, and for the Airmodus A11 nano Condensation Nucleus Counter (nCNC) system, the TSI 3777+3772 Nano Enhancer system, and Aerosol Dynamics Inc.'s (ADI) new versatile water condensation particle counter.Copyright (c) 2018 American Association for Aerosol Research

Coupling photochemistry with flow microreactors enables novel synthesis strategies with higher efficiencies compared to batch systems. Improving the reproducibility and understanding of the photochemical reaction mechanisms requires quantitative tools such as chemical actinometry. However, the choice of actinometric systems which can be applied in microreactors is limited, due to their short optical pathlength in combination with a large received photon flux. Furthermore, actinometers for the characterization of reactions driven by visible light between 500 and 600 nm (e.g. photosensitized oxidations) are largely missing. In this paper, we propose a new visible-light actinometer which can be applied in flow microreactors between 480 and 620 nm. This actinometric system is based on the photoisomerization reaction of a diarylethene derivative from its closed to the open form. The experimental protocol for actinometric measurements is facile and characterized by excellent reproducibility and we also present an analytical estimation to calculate the photon flux. Furthermore, we propose an experimental methodology to determine the average pathlength in microreactors using actinometric measurements. In the context of a growing research interest on using flow microreactors for photochemical reactions, the proposed visible-light actinometer facilitates the determination of the received photon flux and average pathlength in confined geometries. ispartof: SCIENTIFIC REPORTS vol:8 issue:1 ispartof: location:England status: published

The formation rates of 3 nm particles were estimated at SMEAR IV, Puijo (Finland), where the continuous measurements extend only down to 7 nm in diameter. We extrapolated the formation rates at 7 nm (J7) down to 3 nm (J3) based on an approximate solution to the aerosol general dynamic equation, assuming a constant condensational growth rate, a power-law size-dependent scavenging rate, and negligible self-coagulation rate for the nucleation mode particles. To evaluate our method, we first applied it to new particle formation (NPF) events in Hyytiälä (Finland), which extend down to 3 nm, and, therefore, J3 and J7 can be determined directly from the measured size distribution evolution. The Hyytiälä results show that the estimated daily mean J3 values slightly overestimate the observed mean J3, but a promising 91 % of the estimated J3 values are within a factor of 2 from the measured ones. However, when considering detailed daily time evolution, the agreement is not as good due to fluctuations in data as well as uncertainties in estimated growth rates, which are required in order to calculate the time lag between formation of 3 and 7 nm particles. At Puijo, the mean J7 for clear NPF days during April 2007–December 2015 was 0.44 cm−3 s−1, while the extrapolated mean J3 was 0.61 cm−3 s−1., published version, peerReviewed

Nanostructures of platinum-carbon nanocomposite material have been formed by electron-beam induced deposition. These consist of nanodots and nanowires with a minimum size ∼20 nm, integrated within ∼100 nm nanogap n-type silicon-on-insulator transistor structures. The nanodot transistors use ∼20 nm Pt/C nanodots, tunnel-coupled to Pt/C nanowire electrodes, bridging the Si nanogaps. Roomerature single-electron transistor operation has been measured, and single-electron current oscillations and 'Coulomb diamonds' observed. In nanowire transistors, the temperature dependence from 290 to 8 K suggests that the current is a combination of thermally activated and tunnelling transport of carriers across potential barriers along the current path, and that the Pt/C is p-type at low temperature.

We numerically show the advantages of using diamond-on-insulator (DOI) waveguides to design compact supercontinuum (SC) light sources for the visible (VIS) wavelength range. We conclude that the DOI platform is more suitable than silicon nitride waveguides for tailoring the dispersion in such a way that a zero-dispersion wavelength (ZDW) is obtained in the VIS, as is required to achieve efficient VIS SC generation (SCG). After designing a DOI waveguide that features a ZDW at ∼600 nm, we exploit it to numerically obtain a smooth SC ranging from 453 nm to 1030 nm above the -30 dB point after propagation over 4 mm. Our result extends beyond the state-of-the-art shortest VIS wavelengths induced by SCG in integrated waveguides, while using ∼26 times lower input energy and a shorter waveguide length, thus showcasing the potential of the DOI platform for on-chip VIS SC light sources.

Big cat genomes reveal a history of interspecies admixture and adaptive evolution of genes underlying development and sensory perception., The great cats of the genus Panthera comprise a recent radiation whose evolutionary history is poorly understood. Their rapid diversification poses challenges to resolving their phylogeny while offering opportunities to investigate the historical dynamics of adaptive divergence. We report the sequence, de novo assembly, and annotation of the jaguar (Panthera onca) genome, a novel genome sequence for the leopard (Panthera pardus), and comparative analyses encompassing all living Panthera species. Demographic reconstructions indicated that all of these species have experienced variable episodes of population decline during the Pleistocene, ultimately leading to small effective sizes in present-day genomes. We observed pervasive genealogical discordance across Panthera genomes, caused by both incomplete lineage sorting and complex patterns of historical interspecific hybridization. We identified multiple signatures of species-specific positive selection, affecting genes involved in craniofacial and limb development, protein metabolism, hypoxia, reproduction, pigmentation, and sensory perception. There was remarkable concordance in pathways enriched in genomic segments implicated in interspecies introgression and in positive selection, suggesting that these processes were connected. We tested this hypothesis by developing exome capture probes targeting ~19,000 Panthera genes and applying them to 30 wild-caught jaguars. We found at least two genes (DOCK3 and COL4A5, both related to optic nerve development) bearing significant signatures of interspecies introgression and within-species positive selection. These findings indicate that post-speciation admixture has contributed genetic material that facilitated the adaptive evolution of big cat lineages.

In this manuscript we present a radiative transfer model for submerged vegetation called SAILHFlood. It simulates reflectance for a partial submerged canopy from vegetation variables, water level, measurement geometry and soil reflectance. It is a version of the proven SAILH model in which, two vegetation layers are included instead of one: the emerged vegetation layer and the submerged vegetation layer, for which the water attenuation is considered. The model validation was performed with a experiment in laboratory conditions varying leaf area index, water level and illumination and observation angles. A least square linear fit of simulated data used to reproduce measured data shows a satisfactory root mean square error (RMSE) of 0.0355, and a spectral angle of 0.2591 radians. The model could be applied to the diversity of vegetation found in flooded situations, both to understand spectral behavior of these environments under different scenarios and to estimate vegetation variables from model inversion. Fil: Beget, M. E.. Instituto Nacional de Tecnología Agropecuaria; Argentina Fil: Bettachini, Víctor. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Di Bella, Carlos Marcelo. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Baret, F.. Institut National de la Recherche Agronomique; Francia

Laser-produced plasma-induced shock wave in liquid media of different densities has been experimentally studied using non-intrusive diagnostics. A time-resolved Mach–Zehnder interferometer is setup to track the shock wave and subsequent density perturbations in the medium. Two-dimensional spatial distributions for both, ambient medium density and plasma (electron) density have been obtained by employing customised inversion technique and algorithm on the recorded interferograms. It has been observed that the nature of the shock-induced density perturbation in liquid medium is significantly different as compared to that in the gaseous medium. The observed density perturbations have been correlated with the primary shock wave and stress waves reflected from within the target and travelling back in the medium. The trend in the variation of electronic charge density in the plume region has also been studied.

We demonstrate, what is to our knowledge, the shortest pulses directly generated to date from a solid-state laser, mode locked with a graphene saturable absorber (GSA). In the experiments, a low-threshold diode-pumped Cr3+: LiSAF laser was used near 850 nm. At a pump power of 275 mW provided by two pump diodes, the Cr3+: LiSAF laser produced nearly transform-limited, 19-fs pulses with an average output power of 8.5 mW. The repetition rate was around 107 MHz, corresponding to a pulse energy and peak power of 79 pJ and 4.2 kW, respectively. Once mode locking was initiated with the GSA, stable, uninterrupted femtosecond pulse generation could be obtained. In addition, the femtosecond output of the laser could be tuned from 836 nm to 897 nm with pulse durations in the range of 80-190 fs. We further performed detailed mode locking initiation tests across the full cavity stability range of the laser to verify that pulse generation was indeed started by the GSA and not by Kerr lens mode locking., European Research Council (ERC)

Fiber lasers are a fast growing class of lasers due to their reliability, efficiency and flexibility. This has made fiber lasers a versatile tool for manufacturing, sensing and healthcare, not forgetting the contribution of Erbium-doped amplifiers to optical communications. Yet available wavelengths by direct emission are quite restricted to the visible and near infrared wavelength interval (500 nm to 2 micron), with very few offering high power and efficient operation, namely 1 micron, 1.5 micron and 2 micron wavelengths. In this paper we comment on the state of the art and future challenges in the field of fiber lasers to address new wavelength and new applications. In particular to extended the emission interval above 3 micron. This work collects the experience of the COST MP1401 Network on fiber lasers and their application and will present some of the areas were efforts have been focused. More exhaustive material will be presented at the conference.

We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr3+) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr3+ -doped GdLiF4 crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range. (C) 2016 Optical Society of America

We numerically investigate the capabilities and advantages of Raman lasers based on integrated single-crystal diamond ring resonators. To this end, we first model continuous-wave (CW) Raman lasing action while taking into account the lasing directionality, the linear and nonlinear losses, and the coupling of the fields between the bus and ring sections of racetrack-shaped diamond ring resonators. We then consider the design of the ring resonators for a short-wavelength infrared (SWIR) and an ultraviolet (UV) Raman laser. Using our Raman lasing model, we determine the lasing directionality, pump threshold and lasing efficiency of the SWIR and UV devices. We find that both can yield efficient CW operation with SWIR and UV lasing slope efficiencies of 33 % and 65 %, respectively. These results showcase the potential of integrated diamond ring Raman lasers for producing wavelengths that are challenging to generate with other types of integrated lasers.

A compiled set of in situ data is important to evaluate the quality of ocean-colour satellite-data records. Here we describe the data compiled for the validation of the ocean-colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI). The data were acquired from several sources (MOBY, BOUSSOLE, AERONET-OC, SeaBASS, NOMAD, MERMAID, AMT, ICES, HOT, GeP&CO), span between 1997 and 2012, and have a global distribution. Observations of the following variables were compiled: spectral remote-sensing reflectances, concentrations of chlorophyll a, spectral inherent optical properties and spectral diffuse attenuation coefficients. The data were from multi-project archives acquired via the open internet services or from individual projects, acquired directly from data providers. Methodologies were implemented for homogenisation, quality control and merging of all data. No changes were made to the original data, other than averaging of observations that were close in time and space, elimination of some points after quality control and conversion to a standard format. The final result is a merged table designed for validation of satellite-derived ocean-colour products and available in text format. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) were preserved throughout the work and made available in the final table. Using all the data in a validation exercise increases the number of matchups and enhances the representativeness of different marine regimes. By making available the metadata, it is also possible to analyse each set of data separately. The compiled data are available at doi:10.1594/PANGAEA.854832 (Valente et al., 2015).

We show that a significant enhancement of the photon flux produced by high harmonic generation can be obtained through guided configuration at high laser intensity largely above the saturation intensity. We identify two regimes. At low pressure, we observe an intense second plateau in the high harmonic spectrum in argon. At relatively high pressure, complex interplay between strongly time-dependent ionization processes and propagation effects leads to important spectral broadening without loss of spectral brightness. We show that the relevant parameter for this physical process is the product of laser peak power by gas pressure. We compare source performances with high harmonic generation using a gas jet in loose focusing geometry and conclude that the source developed is a good candidate for injection devices such as seeded soft x-ray lasers or free electron lasers in the soft x-ray range.

International audience; The wavefront of an injection-seeded soft x-ray laser beam generated by amplification of high-harmonic pulses in a lambda = 18.9 nm molybdenum plasma amplifier was measured by a Hartmann wavefront sensor with an accuracy of lambda/32 root mean square (rms). A significant improvement in wavefront aberrations of 0.51 +/- 0.03 lambda rms to 0.23 +/- 0.01 lambda rms was observed as a function of plasma column length. The variation of wavefront characteristic as a function time delay between the injection of the seed and peak of soft x-ray amplifier pump was studied. The measurements were used to reconstruct the soft x-ray source and confirm its high peak brightness. (C) 2013 Optical Society of America

International audience; In this work, we report the experimental observation of supercontinua generation in two kinds of suspended-core microstructured soft-glass optical fibers. Low loss, highly nonlinear, tellurite and As2S3 chalcogenide fibers have been fabricated and pumped close to their zero-dispersion wavelength in the femtosecond regime by means of an optical parametric oscillator pumped by a Ti:Sapphire laser. When coupled into the fibers, the femtosecond pulses result in 2000-nm bandwidth supercontinua reaching the Mid-Infrared region and extending from 750 nm to 2.8 mu m in tellurite fibers and 1 mu m to 3.2 mu m in chalcogenide fibers, respectively.

Mobility particle size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers) or SMPS (Scanning Mobility Particle Sizers) have found a wide range of applications in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards and guidelines with respect to the instrumental set-up, measurement mode, data evaluation as well as quality control. Technical standards were developed for a minimum requirement of mobility size spectrometry to perform long-term atmospheric aerosol measurements. Technical recommendations include continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyzer. We compared commercial and custom-made inversion routines to calculate the particle number size distributions from the measured electrical mobility distribution. All inversion routines are comparable within few per cent uncertainty for a given set of raw data. Furthermore, this work summarizes the results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research) and ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) to determine present uncertainties especially of custom-built mobility particle size spectrometers. Under controlled laboratory conditions, the particle number size distributions from 20 to 200 nm determined by mobility particle size spectrometers of different design are within an uncertainty range of around ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. For particles larger than 200 nm, the uncertainty range increased to 30%, which could not be explained. The network reference mobility spectrometers with identical design agreed within ±4% in the peak particle number concentration when all settings were done carefully. The consistency of these reference instruments to the total particle number concentration was demonstrated to be less than 5%. Additionally, a new data structure for particle number size distributions was introduced to store and disseminate the data at EMEP (European Monitoring and Evaluation Program). This structure contains three levels: raw data, processed data, and final particle size distributions. Importantly, we recommend reporting raw measurements including all relevant instrument parameters as well as a complete documentation on all data transformation and correction steps. These technical and data structure standards aim to enhance the quality of long-term size distribution measurements, their comparability between different networks and sites, and their transparency and traceability back to raw data., JRC.H.2-Air and Climate

International audience; The amplification of high-order harmonics (HOH) in a plasma-based amplifier is a multiscale, temporal phenomenon that couples plasma hydrodynamics, atomic processes, and HOH electromagnetic fields. We use a one-dimensional, time-dependent Maxwell-Bloch code to compare the natural amplification regime and another regime where plasma polarization is constantly forced by the HOH. In this regime, a 10-MW (i.e., 100 times higher than current seeded soft x-ray laser power), 1.5-mu J, 140-fs pulse free from the parasitic temporal structures appearing on the natural amplification regime can be obtained.

International audience; Ultrafast dynamics of excited molecules is studied through time-resolved two-vacuum-ultraviolet (vuv)- photon ionization using a nonlinear volume autocorrelator unit. The two-vuv-photon process is induced by the intense fifth harmonic radiation of a femtosecond Ti:sapphire laser. In a proof-of-principle experiment, ultrafast dynamics of excited ethylene and oxygen molecules are investigated. Molecular decay times are deduced by comparing the experimental data with the results of a numerical model that accounts for the spatial and temporal characteristics of the harmonic field. The present experiments pave a convenient way for time domain investigations in the vuv-xuv spectral region in all states of matter at few femtosecond to subfemtosecond temporal scales.

The gain and refractive index dynamics of dilute nitride antimonide semiconductor optical amplifiers are studied using heterodyne pump probe spectroscopy, both in forward and reverse bias regimes. In the forward biased absorption regime, both gain and refractive index relax on the same timescale indicating that both quantities are linked to the same relaxation process, interband recombination. Above transparency, in the forward biased gain regime, the gain and phase exhibit differing timescales resulting in a dynamical alpha factor that varies strongly with time. Reversed bias measurements suggest a recombination dominated absorption recovery where the recovery timescale increases with increasing reversed bias, possibly due to charge separation effects. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3246781]

International audience; Harmonic seeded operation of a neon-like titanium plasma-based soft x-ray laser is described. The plasma amplifier is pumped with a variation of the grazing incidence technique involving a fast and localized ionization step. We discuss its effect on gain dynamics by measuring the amplifying factor as a function of the delay between pump pulse and harmonic seed. Two different regimes are pointed out, following the pumping scheme used. For one of them, a delay in the gain generation compared with the pumping laser pulse is observed. (C) 2015 Optical Society of America

International audience; This paper reviews the major accomplishments in the development of plasma-based soft X-ray lasers and their applications in 2012. Significant experimental breakthroughs include the extension of the lasing range down to 1.5 nm in an X-FEL photoionized plasma and the 100-Hz operation of a 18.9-nm laser with a record average power of 0.15 mW. New fields of applications, exploiting the high-brightness, coherence, and compactness of the source, were demonstrated. Further breakthroughs toward higher peak power are anticipated from numerical simulations of injection-seeded soft X-ray lasers.

Wavelength conversion using an indium phosphide based microdisc laser (MDL) heterogeneously integrated on a silicon-on-insulator waveguide is reported. Several lasing modes are present within the disc cavity, between which wavelength conversion can be performed by mode switching and spectral filtering. For the first time, low-power wavelength up- and downconversion using one single MDL is demonstrated. Operation with a bit error rate below 10(-9) at 2.5 Gbit/s and operation below the forward-error-correction limit of 10(-3) at 10 Gbit/s are shown without the use of additional seeding beams.

International audience; The wavefront of a lambda=18.9 nm soft x-ray beam from an injection-seeded plasma amplifier was measured using a Hartmann sensor. An optical quality superior to that of the seed, up to lambda/7 rms, was obtained. (C) 2013 Optical Society of America

The ablation of solid tin surfaces by an 800-nanometer-wavelength laser is studied for a pulse length range from 500 fs to 4.5 ps and a fluence range spanning 0.9 to 22 J/cm^2. The ablation depth and volume are obtained employing a high-numerical-aperture optical microscope, while the ion yield and energy distributions are obtained from a set of Faraday cups set up under various angles. We found a slight increase of the ion yield for an increasing pulse length, while the ablation depth is slightly decreasing. The ablation volume remained constant as a function of pulse length. The ablation depth follows a two-region logarithmic dependence on the fluence, in agreement with the available literature and theory. In the examined fluence range, the ion yield angular distribution is sharply peaked along the target normal at low fluences but rapidly broadens with increasing fluence. The total ionization fraction increases monotonically with fluence to a 5-6% maximum, which is substantially lower than the typical ionization fractions obtained with nanosecond-pulse ablation. The angular distribution of the ions does not depend on the laser pulse length within the measurement uncertainty. These results are of particular interest for the possible utilization of fs-ps laser systems in plasma sources of extreme ultraviolet light for nanolithography., Comment: 8 pages, 7 figures

With increasing demand for accurate calculation of isotope shifts of atomic systems for fundamental and nuclear structure research, an analytic energy derivative approach is presented in the relativistic coupled-cluster theory framework to determine the atomic field shift and mass shift factors. This approach allows the determination of expectation values of atomic operators, overcoming fundamental problems that are present in existing atomic physics methods, i.e. it satisfies the Hellmann-Feynman theorem, does not involve any non-terminating series, and is free from choice of any perturbative parameter. As a proof of concept, the developed analytic response relativistic coupled-cluster theory has been applied to determine mass shift and field shift factors for different atomic states of indium. High-precision isotope-shift measurements of $^{104-127}$In were performed in the 246.8-nm (5p $^2$P$_{3/2}$ $\rightarrow$ 9s $^2$S$_{1/2}$) and 246.0-nm (5p $^2$P$_{1/2}$ $\rightarrow$ 8s $^2$S$_{1/2}$) transitions to test our theoretical results. An excellent agreement between the theoretical and measured values is found, which is known to be challenging in multi-electron atoms. The calculated atomic factors allowed an accurate determination of the nuclear charge radii of the ground and isomeric states of the $^{104-127}$In isotopes, providing an isotone-independent comparison of the absolute charge radii., Comment: Submitted

International audience; We perform wavefront measurements of high-order harmonics using an extreme-ultraviolet (XUV) Hartmann sensor and study how their spatial properties vary with different generation parameters, such as pressure in the nonlinear medium, fundamental pulse energy and duration as well as beam size. In some conditions, excellent wavefront quality (up to lambda/11) was obtained. The high throughput of the intense XUV beamline at the Lund Laser Centre allows us to perform single-shot measurements of both the full harmonic beam generated in argon and individual harmonics selected by multilayer mirrors. We theoretically analyze the relationship between the spatial properties of the fundamental and those of the generated high-order harmonics, thus gaining insight into the fundamental mechanisms involved in high-order harmonic generation (HHG). (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement